1. Field of the Invention
The present invention relates to an image forming method using an electrophotographic photoconductor, and more particularly to an electrophotographic image forming method comprising the steps of charging the electrophotographic photoconductor to a predetermined polarity by use of a charging member, which may be in contact with the photoconductor, and transferring a developed toner image formed on the photoconductor to an image receiving member using an image transfer charging member, which may be in contact with the photoconductor.
2. Discussion of Background
Various inorganic materials such as Se, CdS and ZnO are conventionally employed as photoconductive materials for an electrophotographic photoconductor However, because of poor photosensitivity, low thermal stability and toxicity of the above-mentioned inorganic materials, electrophotographic photoconductors employing organic photoconductive materials have been actively developed in recent years, and in fact, a variety of organic photoconductors are applied to the commercially available copying machine and printer.
In an image forming method by means of the above-mentioned electrophotographic photoconductor employing the organic photoconductive material, corona discharge which is caused by applying a high voltage to metallic wire is conventionally used in the charging step and the image transfer step.
When the corona discharge is employed, however, ozone and NO.sub.x are generated in the course of the charging and image transfer steps, which will impair the photoconductor comprising the organic materials.
To solve the above-mentioned problem, the inventors of the present invention have proposed an electrophotographic photoconductor with improved resistance to gases such as ozone and NO.sub.x by specifying an oxygen transmission coefficient of a surface top layer of the photoconductor, as disclosed in Japanese Laid-Open Patent Application 8-272126.
However, it is preferable not to generate ozone and NO.sub.x gases from the viewpoints of safety and hygiene. In recent years, therefore, research and development of contact charging or contact image transfer charging by use of a charger in the form of a roller or belt which is disposed in contact with the photoconductor has been conducted instead of the corona charging, and such a contact charging or image transfer charging method is put in practical use.
Although the generation of gases such as ozone and No.sub.x can be efficiently prevented by the contact charging or contact image transfer charging method, pinholes are readily formed in the surface of the photoconductor because the charging or the image transfer charging is carried out with the charger in the form of a roller or belt in contact with the surface of the photoconductor. Further, cracks are often generated on the surface of the photoconductor by the influence of a material bleeding out of the molded charging roller or belt. Thus, there occurs the problem of image defect due to the pinholes and cracks formed on the photoconductor, which has never occurred in the electrophotographic image forming method employing the conventional corona discharge.